Air conditioning or air handling units that include both heating and cooling capabilities are commonplace in modern society. Powerful industrial or commercial air conditioning systems are often utilized to condition (i.e., control the temperature and humidity) the air on the inside of buildings such as office towers, warehouses, factories, and schools. Such air conditioners are often very large in size and require significant amounts of space and energy to effectively handle and condition the air inside such industrial or commercial buildings.
Air conditioning units used for such applications typically include various compartments or sections that are dedicated to either heating or cooling the air stream flowing through the unit. In general, the cooling sections of such units include a compressor, an expansion valve, a heated coil, a chilled coil, a heat transfer gas such as Freon, multiple fans, and a control unit. The compressor, which is a pump, compresses cool Freon gas, causing it to become hot, high pressure, Freon gas. This hot gas moves through a set of coils where it dissipates heat and condenses into a liquid. Heat from this set of coils is dispersed to the outside environment by a fan which blows air across the heated coils. The liquid then passes through an expansion valve and evaporates to become cold, low-pressure Freon gas. The cold gas then runs through a second set of coils where it absorbs heat from the air inside the building. A second fan disperses the cooled air out of the air conditioner and into the space being cooled.
Prior art air conditioning systems, typically referred to as “multi-zone” or “dual-duct” systems, control the temperature of a room by varying the temperature of the air delivered to the room. Such systems are also referred to as “constant volume” systems because they deliver a constant airflow to each zone or room in a building. A primary advantage of constant volume systems is that they provide the desired ventilation, but do not require an excessive number of system parts and do not require complicated control sequences. Despite these advantages, constant volume systems are problematic in that they redirect air from the cooling section to the heating section of the unit. This redirection of air results in the final air supply being delivered to the room without the dehumidifying benefit of the system's cooling coil.
Certain other prior art systems that direct 100% of the air handled by the system through the cooling coil require either (i) an external heat source to reheat the air before it is delivered to a room or zone; or (ii) a method that reduces the airflow known as “Variable Air Volume (VAV).” VAV systems are typically used in spaces where occupancy of the area is variable. Thus, there is a need for an air conditioning unit that utilizes a more efficient means for directing air, and cooled air in particular, through the system.
In many air conditioning units, the condenser coil is located on the outside of the building that the unit is servicing. The heat generated by the coil is vented to the outside environment and any energy present in the form of heat is lost to the environment. Conceivably, this heated air stream could be directed back into the unit, and the energy from the heated air stream could be captured to increase the efficiency of the unit, i.e., increase output and/or reduce energy consumption. Thus, there is also a need for an increased efficiency air conditioning system that is capable of recapturing energy that is typically wasted by prior art systems.
Increased efficiency and/or reduced energy consumption may also be achieved by using certain specialty components within the system or air conditioning unit. One source for increasing efficiency in terms of heat output is the system's heat exchanger. Heat exchangers manufactured from cast iron have been commercially available for many years. Such heat exchangers are typically constructed to include a relatively large combustion chamber and smaller exhaust passageways which are used to increase the surface area of the heat exchanger and create greater heat exchange efficiency. The basic purpose of a large combustion chamber or area is to eliminate impingement of flame directly onto the heat exchanger membrane, thereby increasing the life expectancy of the assembly.
Such heat exchangers are often very large in size and consequently may be impractical for some applications. Additionally, these heat exchangers cannot typically be adapted to different system requirements and configurations. Furthermore, if the heat exchanger cracks or fractures, the entire unit must often be replaced. Thus, there is a need for an increased-efficiency, adaptable, easily serviceable heat exchanger for commercial and residential heating ventilating and cooling systems.